1. Field of the Invention
The present invention relates to a thermo-plastic polyester resin composition having an improved impact resistance. More particularly, relates to a thermoplastic polyester resin composition having an excellent impact resistance, which comprises a thermo-plastic polyester resin and, incorporated therein, a polyorganosiloxane rubber, a specific organic silane compound and optionally, a reinforcing filler.
2. Description of the Related Art
Since a thermoplastic polyester, for example, a polyalkylene terephthalate, has excellent physical properties, heat stability, weatherability and electrically insulating properties, the thermoplastic polyester is widely used for electrical and electronic parts, automobile parts and the like. However, the application fields are considerably restricted because the impact resistance, especially the notched impact strength, is low. Various processes have been proposed for improving the impact resistance of the thermoplastic polyester resin. These processes are satisfactory to some extent in the improvement of the impact strength, but other characteristics are sacrificed, and these processes are not practically applicable. For example, the impact resistance can be improved by incorporating a diene rubber reinforcing resin into a thermoplastic polyester resin, but the heat stability and weatherability are drastically degraded. In contrast, if an acrylic rubber reinforcing resin is incorporated into a thermoplastic polyester resin, reduction of the weatherability is not conspicuous, but no substantial effect of improving the impact strength at low temperatures is obtained. Moreover, incorporation of an olefin copolymer is effective for improving the impact resistance, but other mechanical properties are degraded, or the dispersibility is poor and laminar separation is caused. Accordingly, this process cannot be practically adopted.